Currently, within the framework of the airport phases, the division of onboard/ground control responsibilities, the operational procedures, the traffic density and the significant number of parties on the airport platform do not allow an aircraft to avail itself of equipment having the capability of synthesizing all the information in order to move in an optimal manner.
One solution consists in using the existing systems installed aboard the aircraft such as the flight management system or FMS the acronym standing for the expression Flight Management System, the integrated monitoring system or ISS the acronym standing for the expression Integrated Surveillance System and to enhance them with taxiing assistance functions.
A flight management system comprises in a conventional manner one or more microprocessors linked to a work memory, a program memory, a data storage memory and to an input-output interface, these programs being aimed at ensuring various functions. But the functions accessible via an FMS are insufficient to achieve the objectives of the function:                Location offered by an FMS system is of the order of 100 m while the ground part requires means for positioning of the order of 10 m for the display functions, of the order of 1 m for the alert and guidance assistance functions and less than 1 m for the automatic guidance functions.        Construction of the “taxiing plan” is highly prescribed by the ground control authority or “ATC” the acronym standing for the expression Air Traffic Control and is often incremental and partial as a function of the various control zones distributed over the airport. For example, on large-scale international airports, such as Paris Charles De Gaulle, one controller is in charge of the runway zone, a second the taxiways and a third the passenger boarding zones. The course is then dictated to the pilot as he advances. He stops at the limits of each control zone and cannot cover the whole of the movement, from the runway to the boarding gate (or the reverse journey). In fact, the tools and processes available in an FMS are not appropriate since they are designed to describe the whole of a flight, from takeoff to landing so as to perform all the calculations necessary for the consumption predictions and for the guidance instructions. Additionally, the descriptions of the ground procedures are not standardized, unlike the in-flight procedures which are available onboard from the FMSs through a database arising from data published by the State control bodies.        The aircraft performance database PERF is not suited to the taxiing model.        The lateral trajectory calculation module takes account of the performance of the aircraft while the ground taxiing must take account of the topology of the airport.        The objective of the predictions is to construct a vertical profile that is optimized on the lateral trajectory. On the ground, only the horizontal speed can be adjusted.        The objective of the ground guidance is to present the instructions to be applied manually (except the emergency instructions).        
Likewise, the functions accessible via the ISS are insufficient to achieve the objectives of the function:
the ground monitoring is not taken into account,
the consolidation is not processed between the traffic and terrain situations,
the anticipation functions are based on trajectories computed using the data of the FMS in 3D or 3D+time.
Additionally, certain airport mapping systems, such as those present in EFBs the acronym standing for Electronic Flight Bag (which are applications used by pilots on portable computers to prepare their flights and which do not form part of the onboard avionics) or specific products such as the OANS make it possible:
to display the map of the airport showing the position of the aircraft and its situation with respect to the topology of the airport and to the surrounding structures,
to obtain information on “airport items” by way of the user interface,
to obtain annotations, advice (e.g. “Approaching Runway”).
But these functions ensure only limited monitoring, because they rely exclusively on databases describing the geometry of the airport, whose updating frequency is related only to the alterations in the infrastructures and not to the rules of use dictated (and modified periodically) by the local control authorities; in particular, they are insufficient notably to:
display a map presenting the most variable airport information, such as for example the directions prohibited as a function of the landing direction chosen by the control as a function of the force and direction of the local wind,
process this same dynamic information to assist the crew in viewing or selecting the course elements prescribed by the ground control,
ensure a routing function offering the crew automation of the actions making it possible to chain together the designated course elements and to calculate various relevant parameters, such as an estimate of the fuel consumed for example or indications of directions to the diverse branch-offs encountered and present the course computed as a supplement to the mapping of the infrastructures.
Finally, the role of certain functions, such as the “RAAS” the acronym standing for the expression Runway Awareness and Advisory System from Honeywell, available through the EGPWS product, is to warn the crew during the approach to a runway. They are based on the runway information alone, independently of the possible connections with the taxiways or of their real activity. Moreover, segregation of the equipment used during the taxiing phases prevents these messages from being correlated with course information computed through a routing means or a richer database availing itself of all the information on the airport surface.